Moiré nanophotonics: from fundamental concepts to device engineering

Recent progress in theoretical modeling, numerical simulation, and nanofabrication has established photonic moiré structures as a practical platform for engineering optical bands, localization, and radiation. Moiré photonics refers to optical systems in which a long-wavelength superstructure emerges from controlled mismatch between periodic elements, including relative rotation, lateral shift, or parameter detuning. In this paper, we focus on moiré photonic crystals, especially twisted-bilayer and merged photonic-crystal platforms, where relative twist, stacking, and interlayer coupling act as geometry-level control knobs that reshape optical minibands, momentum-conversion channels, the local density of states, and radiative leakage through band folding, hybridization, and interference. We summarize the construction of commensurate moiré superlattices, the physical mechanisms of moiré scattering and localization, and recent experimental progress in cavities, collective and chiral lasing, cavity quantum electrodynamics, and nonlinear frequency conversion and beam shaping. Throughout, we place moiré nanophotonics within the broader landscape of supercell photonics by comparing them with deterministic supercells, coupled-cavity arrays, and inverse-designed structures. We conclude by outlining the key challenges and opportunities related to scalability, disorder tolerance, leakage control, and real-time reconfigurability.